Functionalized-graphene composites: Fabrication and applications in sustainable energy and environment

Graphene, including pristine graphene and its analogues of graphene oxide and reduced graphene oxide, is revolutionizing the way we design high performance devices, particularly in the areas of sustainable energy and environmental technologies. From environmental remediation and sensing to energy conversions and storage, there are many successful cases of graphene applications. Instead of being a standalone working material, graphene is almost always coupled with another active material as a composite. With its high surface-to-bulk ratio, efficient heat transfer, and electron conduction, the interfacing with graphene not only helps to overcome such limitations in the bare working material but actually accentuates them. To achieve this, the strategy of surface functionalization of graphene, with either soft matters (e.g., organics, molecular linkers, proteins) or solid inorganic matters (e.g., metal nanoparticles, oxide semiconductors), holds the key to enabling the fabrication of high performance composites. The resultant architectures, in which the graphene is applied to, yield the highest achievable properties and should be unique to the specific applications. This Review provides a bottom-up account encompassing the functionalization of graphene to the design of graphene-based composites and also their selected applications in high performance systems relevant to energy and the environment.